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(11) | EP 3 208 853 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | MICRO-CONCENTRATOR MODULE AND DEPLOYMENT METHOD |
| (57) A micro-concentrator module 20 includes a cover glass 22 provided with solar cells
40 on one side thereof. The cover glass is adapted to hover above a substrate 24 containing
an array 24 of MEMS based reflectors. Springs 36 between the cover glass 22 and the
substrate 24 displace the cover glass from a stowed position during transport to a
deployed operational position above the substrate. Tethers 38 connecting the cover
glass with the substrate limit the displacement of the cover glass to a distance corresponding
to the focal length of the reflectors.
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BACKGROUND INFORMATION
1. Field:
[0001] The present disclosure generally relates to solar energy collectors, particularly those employing micro-concentrators, and deals more particularly with a micro-concentrator module that can be stowed and deployed on command.
2. Background:
[0002] MEMS (micro-electromechanical systems) based micro-concentrator modules have been devised that increase solar energy conversion efficiency by employing MEMS controlled reflectors that track and concentrate solar radiation on an array of solar cells. These modules comprise a transparent cover glass spaced above an underlying substrate. An array of solar cells arranged on the underside of a cover glass are aligned with a corresponding array of MEMS based reflectors located on the substrate. The cover glass and underlying substrate are held in fixed, spaced-apart relationship to each other, either by mounting the cover glass and substrate in a rigid frame, or by connecting them with rigid spacers, such as screws located at the corners of the cover glass/substrate. The spacing between the cover glass and substrate is such that the solar cells are respectively positioned at the focal points of the MEMS-based reflectors.
[0003] The MEMS based concentrator modules described above, while effective, have limitations when employed for certain applications, such as solar collectors used by spacecraft in deep space. In spacecraft applications, the spacing required between solar cells and MEMS based reflectors result in a module that requires a relatively large volume of spacecraft during launch. Moreover, known MEMS based concentrator model modules are relatively delicate and may be undesirably affected by compression and/or acoustic loads encountered during spacecraft launch.
[0004] Accordingly, there is a need for MEMS based concentrator modules that may be stowed to displace minimum volumes during launch of a spacecraft, but may be later deployed to operate normally while in deep space. There is also a need for a related method of stowing MEMS based concentrator modules during lunch, and subsequently deploying them while in space.
SUMMARY
[0005] A MEMS-based solar micro-concentrator module has a thin cover glass with miniature solar cells that hover above an array of MEMS based concentrators. In order to survive G-forces and compression/acoustic loads during spacecraft launch, the module is stowed in a collapsed condition. Following launch while in space, the module may be deployed to an expanded operating position, in which a cover glass containing solar cells is displaced away from an underlying substrate containing MEMS based reflectors that concentrate and reflect incident solar radiation onto the solar cells. Leaf springs bias the cover glass away from the underlying substrate during deployment and also act as an electrical connection between the solar cells and a circuit on a substrate that processes electrical power produced by the solar cells. Flexible, collapsible tethers connecting the cover glass with the substrate constrain the cover glass to limit its displacement away from substrate during deployment such that the solar cells are located and held at the focal length of the MEMS based reflectors.
[0006] According to one disclosed example, a micro-concentrator module is provided, comprising a cover glass and a plurality of solar cells located on one side of the cover glass. The cover glass is adapted to hover over a substrate that includes an array of micro-electromechanical systems (MEMS) based reflectors. The module also comprises a plurality of springs connecting the cover glass and the substrate, and a plurality of tethers connecting the cover glass with the substrate.
[0007] According to another disclosed example, a micro-concentrator solar array module is provided comprising a substrate, an array of micro-electromechanical systems (MEMS) based reflectors on the substrate, and a cover glass. The module also includes a plurality of solar cells located on one side of the cover glass, and a plurality of springs biasing the cover glass to shift from a stowed position to a deployed position spaced above the MEMS based reflectors.
[0008] According to still another example, a method is provided of deploying solar cells, comprising stowing a cover glass having solar cells thereon, and deploying the cover glass from a stowed position thereof closely overlying an array of micro-electromechanical systems (MEMS) based reflectors, to a deployed position in which the cover glass is spaced above the array of MEMS based reflectors at a focal length of the MEMS-based reflectors.
[0009] The features, functions, and advantages can be achieved independently in various examples of the present disclosure or may be combined in yet other examples in which further details can be seen with reference to the following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The novel features believed characteristic of the illustrative examples are set forth in the appended claims. The illustrative examples, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative example of the present disclosure when read in conjunction with the accompanying drawings, wherein:
Figure 1 is an illustration of a perspective view of a micro-concentrator module, shown in a deployed condition.
Figure 2 is an illustration of an exploded, perspective view of the micro-concentrator module shown in Figure 1.
Figure 3 is an illustration of a fragmentary, perspective view of a portion of the bottom side of the cover glass forming part of the micro-concentrator module in Figures 1 and 2, showing the solar cells.
Figure 4 is an illustration of a fragmentary, perspective view showing the configuration of the array of MEMS based concentrators on the substrate.
Figure 5 is an illustration of a diagram showing how the mirrors of one of the MEMS based micro-concentrators may be repositioned to maintain reflection of incident light at a focal point on a solar cell.
Figure 6 is an illustration of a plan view of the cover glass showing one subarray of solar cells and bus bars connected to the solar cells, the remaining arrays of solar cells not shown for clarity.
Figure 7 is an illustration of a cross-sectional view of the micro-concentrator module in its collapsed, stowed condition, taken along the line 7-7 in Figure 6.
Figure 8 is an illustration similar to Figure 7, but showing the micro-concentrator module in its expanded, deployed condition.
Figure 8A is an illustration area of the area designated as "FIG. 8A" in Figure 8.
Figure 9 is an illustration of a flow diagram of a method of deploying solar arrays.
Figure 10 is an illustration of a flow diagram of aircraft production and service methodology.
Figure 11 is an illustration of a block diagram of an aircraft.
DETAILED DESCRIPTION
[0011] Referring first to Figures 1 and 2, a deployable micro-concentrator solar module (MCM) 20 broadly comprises a substantially flat, transparent cover glass 22, an array of solar cells 40, an array 24 of MEMS based mirrors or reflectors and a substrate such as, without limitation, a printed wiring board (PWB) 26. The array of MEMS based reflectors 24 is located on the top side of the PWB 26. The bottom side of the PWB 26 contains electrical circuit traces 44 and electronic components, including an application specific integrated circuit (ASIC) 42 which controls the MCM module 20, including the collection and processing of electrical power generated by the solar cells 40. A damping pad 28 is mounted on and extends along the outer perimeter of the PWB 26, surrounding the MEMS based reflectors 24.
[0012] A plurality of springs, such as, without limitation, leaf springs 36 are connected between the bottom side of the cover glass 22 and the underlying printed wiring board 26. In the illustrated example, four of the leaf springs 36 are respectively located generally at the four corners of the MCM module 20, however it may be possible in other examples to use as few as three or greater than four of the leaf springs 36. The leaf springs may be formed of any suitable electrically conductive spring material, such as for example, beryllium copper (BeCu) spring wire. As will be discussed later in more detail, the leaf springs 36 bias the cover glass 22 to move away from the PWB 26 from a stowed position, to a deployed position (Figure 1) in which the cover glass 22 is spaced from and hovers above the PWB 26, such that the solar cells 40 are respectively positioned at the focal length of the MEMS based reflector array 24. Once deployed, the leaf springs 36 support the cover glass 22 on the PWB 26.
[0013] The MCM module 20 further comprises a plurality of flexible, collapsible tethers 38 between the PWB 26 and the cover glass 22. In the illustrated example, four of the tethers 38 are respectively located generally at the corners of the MCM module 20 adjacent the leaf springs 36, however in other examples, as few as three or more than four of the tethers 38 may be employed, provided that they maintain the cover glass 22 in substantially parallel relationship to the MEMS based reflector array 24 after the deployment. Each of the tethers 38 has a length that is related to the focal length FL (see Figure 8) of the MEMS based reflector array 24. The tethers 38 function to restrain and thereby limit movement of the cover glass 22 during its deployment to a predetermined distance which is related to the focal length FL. By deploying the cover glass 22 at this predetermined distance from the PWB 26, the radiation reflected by the reflectors in the MEMS based reflector array 24 converges at, and is concentrated on the solar cells 40, thereby maximizing the amount of incident radiation 52 (Figure 5) that is converted into electrical energy by the MCM module 20. The tethers 38 may comprise, for example and without limitation, thin strips of flexible, collapsible film formed of a material suitable for the application. Each of the tethers 38 has its opposite ends attached, as by adhesive bonding respectively to the PWB 26 and the bottom side 48 of the cover glass 22. In one example suitable for deep space environments, the tethers 38 may comprise, for example and without limitation, a polyimide film sold under the trademark black Kapton® or a multifilament yarn spun from a thermoplastic liquid crystal polymer sold under the trademark Vectran®.
[0014] The damping pad 28 may be formed of a suitable foam or a similar shock absorbing, dampening material. For example and without limitation, the damping pad 28 may comprise a polyimide foam, such as one sold under the trademark Solimide®, or similar polyimide open cell foam, having a width and thickness suitable for the application. The damping pad 28 extends around the perimeter of the MCM module 20, surrounding the MEMS based reflector array 24. In the illustrated example, the damping pad 28 is discontinuous strip, having interruptions 45 within which the leaf springs 36 and tethers 38 are located. However, in other examples, the damping pad 28 may be a continuous strip, in which case the leaf springs 36 and tethers 38 may be located inboard of the damping pad 28. In still other examples, the damping pad 28 may comprise a plurality of individual pad-like cushions distributed around the perimeter of the PWB 26, and aligned beneath the outer perimeter of the overlying cover glass 22. In the stowed condition of the MCM module 20, the damping pad 28 is sandwiched between the PWB 26 and the cover glass 22, and functions to absorb acoustic and/or mechanical vibrations imposed on the MCM module 20, as may occur during spacecraft launch. The damping pad 28 also supports the cover glass in spaced relationship above the array 24 of reflectors when the cover glass 22 is stowed.
[0015] Referring now to Figures 1-3 and 6, the solar cells 40 are located on the bottom side 48 (Figure 3) of the cover glass 22, and in the illustrated example, are arranged in a grid of fifteen sub-arrays 35 (see Figure 6), each containing thirty of the solar cells 40. In other examples, more or fewer subarrays 35 and solar cells 40 may be employed. The solar cells 40 in each of the sub-arrays 35 are electrically coupled with each other by electrical circuit traces or interconnects 30 formed on the bottom side 48 of the cover glass 22. In some examples, each of the solar cells 40 may include a lens-like optical element 46 (Figure 3) that functions to concentrate incident solar radiation on the solar cells 40. As will be discussed below in connection with Figures 7 and 8, actuators 75 having plungers 75a may engage the top side 50 of the cover glass to maintain the MCM module in its stowed condition until ready for deployment.
[0016] Referring to Figures 4 and 5, the MEMS based reflector array 24 comprises a plurality of mirror-like reflectors 24a that may be individually tilted and displaced as needed in order to reflect incident radiation 52 passing through the transparent cover glass 22 and focus the reflected radiation on a corresponding one of the corresponding solar cells 40. As previously discussed, by positioning the cover glass 22 a predetermined distance from the PWB 26, the reflected radiation converges to a focal point corresponding to the location of the solar cell 40, thereby maximizing the amount of radiation impinging upon the solar cell 40.
[0017] As shown in Figures 1, 2 and 6, first and second bus bars 32, 34 comprising electrical traces, are located on the bottom side 48 of the cover glass 22. The bus bars 32, 34 are coupled with the electrical interconnects 30 in each sub-array 35 of the solar cells 40, and function to collect the electrical energy generated by the solar cells 40. As will be discussed below, the electrical energy collected by the bus bars 32, 34 are delivered through the electrically conductive leaf springs 36 to the PWB 26 for processing. The use of the leaf springs 36 as flexible electrical connections between the cover glass 22 and the PWB 26 eliminates the need for separate wire connections between the cover glass 22 and the PWB 26.
[0018] Attention is now directed to Figures 7 and 8 which respectively show the MCM module 20 in its stowed and deployed conditions, wherein the MCM module 20 is mounted on an underlying panel 54. The PWB 26 is electrically connected to electrical power and data traces (not shown) on top of the panel 54 by welds 56. In its stowed position, the cover glass 22 is closely spaced from the PWB 26, and the periphery of the cover glass 22 is held against the damping pad 28. A later discussed force applicator 75 holds the cover glass 22 against movement to its deployed position by the leaf springs 36. As can be seen in Figure 7, prior to deployment, the leaf springs 36 are compressed and the tethers 38 are collapsed. During spacecraft launch or vehicle transport, the damping pad 28 absorbs/damps shock and/or vibration, thereby preventing damage to the cover glass 22, leaf springs 36 and other components of the MCM concentrator module 20.
[0019] Referring now particularly to Figure 8 and 8A, the upper end 36a of each of the leaf springs 36 is connected as by a weld 55 to one of the bus bars 32, 34 (Figures 1-3). The opposite end 36b of each of the leaf springs 36 is likewise connected by a weld 55 to circuit traces (not shown) on the PWB 26. Alternatively, the opposite ends 36a, 36b may be mechanically and electrically connected to the bus bars 32, 34 and the PWB 26 by soldering, riveting or other known techniques. The leaf springs 36 thus act as an electrical connection between the array of solar cells 40 on the cover glass 22 and electrical circuitry on the PWB 26.
[0020] In use, prior to vehicle launch or transport, the cover glass 22 is pushed down toward the PWB 26 either manually or by an automated force applicator 75. The force applicator 75 may comprise, for example and without limitation, a suitable electrical, pneumatic, or hydraulic actuator (not shown). Alternatively, the force applicator 75 may comprise another overlying MCM module (not show) forming part of a solar panel array (not shown) that unfolds and moves away from the MCM module 20 when the solar panel array is deployed. When the MCM concentrator module 20 is ready for use (deployment), the force applicator 75 is de-actuated, thereby removing the force that maintains the module 20 in its stowed condition. In the solar panel array example described above, unfolding of the solar panels releases the cover glass 22, allowing it to move away from the underlying PWB 26. With the force applicator 75 de-actuated, the biasing influence of the leaf springs 36 causes displacement of the cover glass 22 upwardly away from the PWB 26. As the cover glass 22 moves upwardly, the tethers 38 unfold and extend. When the tethers 38 are fully extended and tensioned as a result of the force applied to the cover glass 22 by the leaf springs 36, the tethers 38 to restrain the cover glass 22 against further movement. It should be noted here that during the deployment, the cover glass 22 translates in a slight arc as it moves away from the PWB 26 to its deployed position. However, once deployed, the cover glass 22 is precisely positioned relative to the PWB 26, with solar cells 40 aligned above the MEMS based reflector array 24 at the focal length "FL" (Figure 8) of the MEMS based reflector array 24. After deployment, the leaf springs 36 function as electrical connections between the solar cells 40 and a PWB 26 as well as support the cover glass 22 on the PWB 26.
[0021] Figure 9 broadly illustrates a method of deploying solar cells 40. At 62, a cover glass 22 having solar cells 40 thereon is stowed. For example, the cover glass 22 may be stowed in close proximity to an array 24 of underlying MEMS based reflectors. At 64, the cover glass 22 is deployed from its stowed position closely overlying an the array 24 of MEMS based reflectors, to a deployed position in which the solar cells 40 are spaced above the array at a focal length of the reflectors.
[0022] Examples of the disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace, marine, automotive applications and other application where solar collectors are mounted on vehicles, such as, without limitation, spacecraft. Thus, referring now to Figures 10 and 11, examples of the disclosure may be used in the context of a spacecraft manufacturing and service method 66 as shown in Figure 10 and a spacecraft 68 shown in Figure 11. Spacecraft applications may include, for example, without limitation, MCM concentrator modules, comprising arrays of solar cells. During pre-production, exemplary method 66 may include specification and design 70 of the spacecraft 68 and material procurement 72. During production, component and subassembly manufacturing 74 and system integration 76 of the spacecraft 68 takes place. Thereafter, the spacecraft 68 may go through certification and delivery 78 in order to be placed in service 80. While in service by a customer, the spacecraft 68 is scheduled for routine maintenance and service 82, which may also include modification, reconfiguration, refurbishment, and so on.
[0023] Each of the processes of method 66 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of spacecraft manufacturers or major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, or suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.
[0024] As shown in Figure 11, the spacecraft 68 produced by exemplary method 118 may include an airframe 84 with a plurality of systems 86 and an interior 88. Examples of high-level systems 86 include one or more of a propulsion system 90, an electrical system 92, a hydraulic system 94 and an environmental system 96. Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the marine and automotive industries.
[0025] Systems and methods embodied herein may be employed during any one or more of the stages of the production and service method 66. For example, components or subassemblies corresponding to production process 74 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the spacecraft 68 is in service. Also, one or more apparatus examples, method examples, or a combination thereof may be utilized during the production stages 74 and 76, for example, by substantially expediting assembly of or reducing the cost of a spacecraft. Similarly, one or more of apparatus examples, method embodiments, or a combination thereof may be utilized while the spacecraft 68 is in service, for example and without limitation, to maintenance or service 82.
[0026] Further, the disclosure comprises examples according to the following clauses:
Clause 1: A micro-concentrator module, comprising: a cover glass; a substrate including an array of micro-electromechanical systems (MEMS) based reflectors; a plurality of solar cells located on one side of the cover glass and adapted to hover over the array; a plurality of springs connecting the cover glass and the substrate; and a plurality of tethers connecting the cover glass with the substrate.
Clause 2: The micro-concentrator module of Clause 1, wherein the reflectors have a focal length, and each of the tethers has a length that is related to the focal length of the reflectors.
Clause 3: The micro-concentrator module of any one of Clauses 1 or 2, wherein each of the springs is a leaf spring.
Clause 4: The micro-concentrator module of any one of Clauses 1-3, wherein the reflectors are arranged on the substrate, and the plurality of springs are disposed between and coupled with the cover glass and the substrate.
Clause 5: The micro-concentrator module of any one of Clauses 1-4, wherein: the cover glass has an electrical circuit thereon, the substrate has an electrical circuit thereon, the plurality of springs are electrically conductive and are electrically coupled with the electrical circuit on the cover glass with the electrical circuit on the substrate.
Clause 6: The micro-concentrator module of any one of Clauses 1-5, wherein the plurality of springs are disposed around a perimeter of the substrate and support the cover glass above the array.
Clause 7: The micro-concentrator module of any one of Clauses 1-6, wherein each of the tethers is a strip of collapsible film having first and second ends respectively attached to the cover glass and to the substrate.
Clause 8: The micro-concentrator module of any one of Clauses 1-7, wherein the plurality of tethers are disposed around a perimeter of the substrate.
Clause 9: A micro-concentrator solar array module, comprising: a substrate; an array of micro-electromechanical systems (MEMS) based reflectors on the substrate; a cover glass; a plurality of solar cells located on one side of the cover glass; and a plurality of springs biasing the cover glass to shift from a stowed position to a deployed position spaced above the array.
Clause 10: The micro-concentrator solar array module of Clause 9, wherein each of the springs is a leaf spring.
Clause 11: The micro-concentrator solar array module of Clause 9 or 10, further comprising a damping pad sandwiched between the cover glass and the substrate.
Clause 12: The micro-concentrator solar array module of any one of Clauses 9-11, wherein each of the springs is electrically conductive and forms an electrical connection between the cover glass and the substrate.
Clause 13: The micro-concentrator solar array module of any one of Clauses 9-12, further comprising: a plurality of flexible tethers having opposite ends respectively attached to the cover glass and to the substrate, for limiting movement of the cover glass away from the substrate to the deployed position thereof.
Clause 14: The micro-concentrator solar array module of Clause 13, wherein each of the tethers comprises: polyimide film, or multifilament yarn spun from a liquid crystal polymer.
Clause 15: The micro-concentrator solar array module of any one of Clauses 9-14, wherein: the cover glass includes a first electrical trace electrically coupling the solar cells together, the substrate includes a second electrical circuit thereon for processing electrical power produced by the solar cells, and each of the springs is a leaf spring having opposite ends respectively electrically coupled with the first electrical trace and second electrical trace.
Clause 16: A method of deploying solar cells, comprising: stowing a cover glass having solar cells thereon; and deploying the cover glass from a stowed position thereof closely overlying an array of micro-electromechanical systems (MEMS) based reflectors, to a deployed position in which the cover glass is spaced above the array at a focal length of the reflectors in the array.
Clause 17: The method of Clause 16, wherein deploying the cover glass is performed using springs to force the cover glass away from the MEMS based reflectors.
Clause 18: The method of Clause 16 or 17, wherein deploying the cover glass includes laterally translating the cover glass to a position in which the solar cells are aligned with the reflectors.
Clause 19: The method of any one of Clauses 16-17, wherein deploying the cover glass includes limiting movement of the cover glass away from the reflectors to a distance related to the focal length of the reflectors.
Clause 20: The method of any one of Clauses 16-18, wherein limiting movement of the cover glass include using tethers to restrain movement of the cover glass to a distance that is related to the focal length of the reflectors.
[0027] As used herein, the phrase "at least one of", when used with a list of items, means different combinations of one or more of the listed items may be used and only one of each item in the list may be needed. For example, "at least one of item A, item B, and item C" may include, without limitation, item A, item A and item B, or item B. This example also may include item A, item B, and item C or item B and item C. The item may be a particular object, thing, or a category. In other words, at least one of means any combination items and number of items may be used from the list but not all of the items in the list are required.
[0028] The description of the different illustrative examples has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the examples in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative examples may provide different advantages as compared to other illustrative examples. The example or examples selected are chosen and described in order to best explain the principles, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various examples with various modifications as are suited to the particular use contemplated.
a cover glass (22);
a substrate (24) including an array (24) of micro-electromechanical systems (MEMS) based reflectors;
a plurality of solar cells (40) located on one side of the cover glass (22) and adapted to hover over the array (24);
a plurality of springs (36) connecting the cover glass (22) and the substrate (26); and
a plurality of tethers (38) connecting the cover glass(22) with the substrate (26).
the cover glass (22) has an electrical circuit thereon,
the substrate (24) has an electrical circuit thereon, and
the plurality of springs (36) are electrically conductive and are electrically coupled with the electrical circuit on the cover glass (22) with the electrical circuit on the substrate (26).
a substrate (26);
an array (24) of micro-electromechanical systems (MEMS) based reflectors on the substrate (26);
a cover glass (22);
a plurality of solar cells (40) located on one side of the cover glass (22); and
a plurality of springs (36) biasing the cover glass (22) to shift from a stowed position to a deployed position spaced above the array (24),
wherein each of the springs (36) is preferably a leaf spring.a plurality of flexible tethers (36) having opposite ends respectively attached to the cover glass (22) and to the substrate (26), for limiting movement of the cover glass (22) away from the substrate (26) to the deployed position thereof,
wherein each of the tethers (36) preferably comprises:
polyimide film, or
multifilament yarn spun from a liquid crystal polymer.
the cover glass (22) includes a first electrical trace electrically coupling the solar cells (40) together,
the substrate includes a second electrical circuit thereon for processing electrical power produced by the solar cells (40), and
each of the springs (36) is a leaf spring having opposite ends respectively electrically coupled with the first electrical trace and second electrical trace.
stowing a cover glass (22) having solar cells (40) thereon; and
deploying the cover glass (22) from a stowed position thereof closely overlying an array (24) of micro-electromechanical systems (MEMS) based reflectors, to a deployed position in which the cover glass (22) is spaced above the array (24) at a focal length of the reflectors in the array.